JP3179160B2 - Semiconductor device and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a substrate device for driving a flat light valve used in a direct-view display device or a projection display device. More specifically, the present invention relates to a semiconductor integrated circuit substrate device in which a pixel electrode group, a switch element group, and a drive circuit element group are formed on a semiconductor silicon single crystal film on an electrically insulating material. This substrate device is integrated into a liquid crystal panel, for example, to constitute a so-called active matrix device.

[0002]

2. Description of the Related Art Conventionally, an active matrix device deposits an amorphous silicon or polycrystalline silicon layer on an electrically insulating substance, for example, a transparent glass substrate or a transparent quartz substrate, and forms a pixel electrode group on the amorphous silicon or polycrystalline silicon. , And some or all of the switch element group and the drive circuit element group. However, no attempt has been made to form all of the pixel electrode group, the switch element group, and the drive circuit element group on the semiconductor silicon single crystal film on the electrically insulating material.

[0003]

There are two problems to be solved by the present invention. One is a leakage current of a switching transistor due to light, and the other is an operation of a driver circuit formed on single crystal silicon on an electrically insulating material.

In a semiconductor device for a light valve substrate using a liquid crystal, a region where a pixel electrode group is formed is irradiated with light through the liquid crystal. Usually, each switching transistor for selectively supplying power to the pixel electrode group is formed at a location very close to the corresponding pixel electrode. For this reason,
Even if an attempt is made to block light only in a certain region of each switching transistor, some light enters the switching transistor region due to the sneak of light applied to the pixel electrode portion. When light is irradiated into single-crystal silicon, the amount of electron-hole pairs generated in single-crystal silicon varies somewhat depending on the wavelength of light, but a large amount of electrons
Generate a pair of holes. Switching transistor is MO
If the transistor is an S-type transistor, one of the electrons and holes flows into the drain electrode and the other flows into the substrate electrode, resulting in a leakage current. If this leakage current is large, the ON / OFF ratio of the drain current when the switching transistor is ON and OFF (hereinafter simply referred to as ON / OFF ratio)
Abbreviated as ratio. ) Cannot be obtained, and a semiconductor device for a light valve substrate having a high contrast ratio cannot be obtained.

[0005] In addition, single crystal silicon (SOI: Silicon On Insulator) on an electrically insulating material usually has a thickness of
Those in the range of hundreds of angstroms to about 2 microns are often used. A complementary metal oxide semiconductor circuit (hereinafter, CM) formed in normal single crystal silicon
Abbreviated as OS circuit. ) May not operate if it is formed on a thin silicon layer of an SOI wafer as it is. This is because when the silicon thickness of the SOI wafer is too thin, when the potential of a certain position of the silicon substrate is to be fixed, and when the potential of the substrate is to be taken at a contact electrode located at a certain distance from the position, the resistance between the substrate and the contact is reduced. Is too high to fix the substrate potential firmly.

The present invention has the two problems described above, namely, a leakage current (hereinafter referred to as a light leakage current) generated when light from a switching transistor is irradiated and a high resistance between a substrate and a contact of a driver circuit portion. The purpose is to solve resistance.

[0007]

In order to reduce the light leakage current of a switching transistor, the volume of single crystal silicon on an electrically insulating material in a region where the switching transistor is formed may be reduced. If the current value when the switching transistor is ON is determined to a certain value, the length and width of the transistor are determined to a certain value. Therefore, in order to reduce the volume of silicon, the thickness of single crystal silicon in a region where the switching transistor is formed may be reduced.

In order to operate a driver circuit composed of a CMOS circuit formed on single crystal silicon on an electrically insulating material, a thick oxide film (hereinafter abbreviated as a field oxide film) for element isolation between transistors. )), So that silicon with a certain thickness or more remains. That is,
The present invention is characterized in that the thickness of silicon in a region where a driver circuit is formed is larger than the thickness of silicon in a region where a switching transistor is formed.

[0009]

As a result, in the semiconductor device for a light valve substrate according to the present invention, the light leakage current of the switching transistor for selectively supplying power to the pixel electrode group is small, and hence the ON state is reduced.
A switching transistor having a high / OFF ratio can be obtained. Further, a driver circuit comprising a CMOS circuit formed on single crystal silicon on an electrically insulating material easily operates.

Hereinafter, the present invention will be described in detail with reference to the drawings.

[0011]

FIG. 2 is a perspective view showing the structure of a semiconductor device for a light valve substrate which is an active matrix type device. 21 is a silicon oxide film (SiO ₂ film) as an electrically insulating substrate,
Reference numeral 22 denotes a semiconductor single crystal silicon film on the electrically insulating substrate 21. Reference numeral 23 denotes a drive electrode for driving each pixel, and no opaque single crystal silicon remains below the drive electrode 23. Reference numeral 24 denotes a switching transistor for selectively supplying power to the drive electrode of each pixel. FIG.
Then, this switching transistor is a field-effect MO
It consists of S transistors. Reference numeral 25 denotes a signal line connected to the drain electrode of each switching transistor 24. Reference numeral 26 denotes a scanning line connected to the gate electrode of each switching transistor. Reference numeral 27 denotes an X driver that supplies a signal to each signal line 25, and reference numeral 28 denotes a Y driver that supplies a signal to each scanning line 26. Drive electrode 2 for each pixel
3. The switching transistor 24, the signal line 25, the scanning line 26, the X driver 27, and the Y driver 28 are formed in the semiconductor single crystal silicon film 22 or on the semiconductor single crystal silicon film 22 via the insulating film. .

FIG. 3 is a sectional view of the semiconductor device for a light valve substrate in a region surrounded by a broken line 29 in FIG. In FIG. 3, the right half represents a pixel portion, and the left half represents a driver circuit portion. 31
Is a silicon oxide film (SiO ₂ film) that is an electrically insulating substance
Is shown. 32 is a P-well made of a thin P-type impurity in a semiconductor single crystal silicon film, 33 is a drain electrode, 34 is a source electrode, 35 is a gate electrode made of polycrystalline silicon, and 36 is a gate insulating film made of a SiO ₂ film. And a switching transistor composed of a field-effect transistor is formed therefrom. Here, the drain electrode 33 is connected to the signal line 314 formed of aluminum. Further, the gate electrode 35 also functions as the scanning line 26 passing through the pixel portion. Reference numeral 37 denotes a driving electrode of a pixel portion made of polycrystalline silicon thin enough to maintain transparency, and is directly connected to a source electrode of the switching transistor. 38 is a gate electrode 35, 312 made of polycrystalline silicon and a metal layer 31 made of aluminum.
4 is an SiO ₂ film deposited for electrical isolation.
318 is the gate electrode 3 of the switching transistor.
5 is a thin SiO ₂ film deposited for electrical isolation between the pixel 5 and the drive electrode 37 of the pixel portion. 39 is for element isolation,
This is a thick SiO ₂ film formed by thermally oxidizing single crystal silicon, and is hereinafter referred to as a field oxide film.

Next, a part of the configuration of the driver circuit will be described. 32 'is an N well made of a thin N-type impurity in the single crystal silicon film, 310 and 311 are a source electrode and a drain electrode made of a high concentration P-type impurity, respectively.
2 denotes a gate electrode made of polycrystalline silicon, and 313 denotes a gate insulating film made of a silicon oxide film. From these, a P-type field effect MOS transistor is formed. The left half of FIG. 3 shows only a part of the driver circuit portion. In FIG. 3, the potential of the drain electrode 311 of the P-type transistor of the driver circuit portion is set to the substrate (here, N
In order to make the potential of the well 32 ') the same as that of the aluminum 31',
4 is connected to an N ⁺ region 315 in which N-type impurities of the same type as the substrate are formed at a high concentration. However, if the single-crystal silicon region 316 under the field oxide film is extremely thin, the portion has a high resistance, making it difficult to make the potential of the drain electrode of the P-type transistor and the N-well substrate the same. At this time, the driver circuit becomes difficult to move. Therefore, it is necessary to make the thickness of the single crystal silicon region 316 under the field oxide film of the driver circuit portion a certain value or more, and to lower the resistance of the region. Therefore, in FIG. 3, the N-type transistor portion of the pixel portion and the P-type
The thickest value ts of the thickness of the single crystal silicon in the type transistor portion needs to be at least a certain value at least in the driver circuit portion.

Reference numeral 317 denotes an opaque film under the electrically insulating material 31, for example, chromium. This chromium film is provided on the entire lower surface of the driver circuit section via the electrically insulating substance 31. Further, in the pixel portion, similarly, it is provided below each switching transistor in the pixel portion via the electrically insulating substance 31. In the light valve substrate type semiconductor device, although not shown in the drawings, a liquid crystal is provided below the pixel portion, and light is transmitted through the liquid crystal. When this light is applied to the switching transistor and many transistors in the driver circuit section, the electron-hole pairs excited by the light become a leak current, deteriorating the element characteristics. The chromium film 317 provided below the electrically insulating material is provided to prevent light from being irradiated to each transistor.

FIG. 4 is a sectional view of a switching transistor in the pixel portion. 41 is an electrically insulating substance having a thickness of about 1
μm SiO ₂ film, 42 is SiO which is an electrically insulating substance
₂ semiconductor single crystal silicon formed in an island shape on the film 41;
43 and 44 are a source electrode and a drain electrode of the N-type MOS transistor, 45 is a gate electrode made of a polycrystalline silicon film, and 46 is a gate oxide film made of SiO ₂ . A broken line 47 indicates a boundary of a depletion layer generated when a positive voltage is applied to the drain electrode 44 and the gate electrode 45. The depletion layer occurs above and to the right of the dashed line 47.
Reference numeral 48 denotes incident light, and reference numerals 49 and 410 denote electrons and holes generated in the depletion layer by the incident light 48, respectively. The electrons 49 generated by the light reach the drain electrode by the electric field in the depletion layer, and become a drain current. On the other hand, holes reach the substrate electrode if it is nearby, but if not, they accumulate near the boundary 47 of the depletion layer, lower the potential barrier between the source and the substrate, and also play the role of extracting electrons from the source electrode. I will. The electron-hole pairs generated in the depletion layer by light in this way increase the leakage current and serve to lower the transistor characteristics, particularly the ON / OFF ratio.

In order to reduce the leak current due to this light,
The volume of silicon in which the transistor is formed may be as small as possible. However, when a desired current value of the transistor is determined, the length and width of the transistor are naturally determined. In that case, the volume of silicon can be reduced by reducing the thickness of silicon in a region where the transistor is formed. That is, the thickness ts of the silicon shown in FIG.

FIG. 5 shows the relationship between the drain current and the gate voltage at the time of light irradiation and at the time of OFF. The broken line shows the characteristics at the time of light irradiation, and the solid line shows the characteristics at the time of light OFF. When the gate voltage becomes a sufficiently large value and a sufficiently large current value flows through the channel of the transistor, the current value at the time of light irradiation becomes equal to the current value at the time of OFF. Here, the light leakage current drain current i _OL at the light irradiation when the gate voltage V _G is zero
And

FIG. 6 shows the measurement results of the light leakage current i _OL and the silicon thickness ts when light of the same intensity is irradiated when the thickness of the silicon of the MOS transistor having the same length and width is changed. . As expected, the light leakage current decreases as the silicon thickness ts decreases. As described above, in the semiconductor device for a light valve substrate according to the present invention, the switch element group for selectively supplying power to the pixel electrode group, that is, the silicon thickness in the region where the MOS transistor is formed is used to drive the switch element group. It is characterized in that it is thinner than the silicon thickness in the region where the drive circuit element group is formed.

FIG. 1 is a sectional view of a semiconductor device for a light valve substrate according to the present invention in a region surrounded by a broken line 29 in FIG. As in the case of FIG. 3, in FIG. 1, the right half represents the pixel portion, and the left half represents the driver circuit portion. In FIG. 1, reference numeral 11 denotes a silicon oxide film (SiO ₂ film) which is an electrically insulating substance. 12 is a P well made of a thin P-type impurity in a semiconductor single crystal silicon film, 13 is a drain electrode, 14 is a source electrode, 15 is a gate electrode made of polycrystalline silicon,
Reference numeral 16 denotes a gate insulating film made of a SiO ₂ film, from which a switching transistor made of a field-effect MOS transistor is formed. Where 1
The drain electrode 3 is connected to the signal line 114 formed of aluminum. The 15 gate electrodes also serve as scanning lines 26 passing through the pixel portion. Reference numeral 17 denotes a driving electrode of a pixel portion made of polycrystalline silicon thin enough to maintain transparency, and is directly connected to a source electrode of the switching transistor. Reference numeral 18 denotes an SiO ₂ film deposited for electrical isolation between the gate electrodes 15 and 112 and the metal layer 114 made of aluminum. Reference numeral 118 denotes a thin SiO ₂ film deposited for electrical isolation between the gate electrode 15 of the switching transistor and the drive electrode 17 of the pixel portion. 19
Is a thick SiO ₂ film formed by thermally oxidizing single-crystal silicon for element isolation, and is called a field oxide film.

Next, a part of the configuration of the driver circuit will be described. 12 'is an N well made of a thin N-type impurity in the single crystal silicon film, 110 and 111 are a source electrode and a drain electrode made of a high concentration P-type impurity, respectively.
2 denotes a gate electrode made of a polycrystalline silicon film, and 113 denotes a gate insulating film made of a silicon oxide film. From these, a P-type field effect MOS transistor is formed. Although the left half of FIG. 1 shows only a part of the driver circuit portion, the potential of the drain electrode 111 of the P-type transistor in the driver circuit portion is set to be the same as the potential of the substrate (here, the N well 12 ′). Aluminum 1
14 connects to an N ⁺ region 115 in which N-type impurities of the same type as the substrate are formed at a high concentration.

In the semiconductor device for a light valve substrate of the present invention shown in FIG. 1, as shown in FIG. 1, the silicon thickness t _S1 of the driver circuit portion is equal to the silicon thickness t _{s2 of the} portion where the switching transistor is formed in the pixel portion. Thicker. Therefore, the thickness of the silicon layer 116 under the field oxide film formed in the driver circuit portion can be made a certain value or more, the resistance at that location can be sufficiently reduced, and the drain electrode of the P-type transistor can be connected to The N-well substrate can be set to the same potential.

Reference numeral 117 denotes an opaque film under the electrically insulating material 11, for example, chromium. This chromium film is provided on the entire lower surface of the driver circuit section via the electrically insulating substance 11. In the pixel portion, similarly, it is provided below each switching transistor in the pixel portion via the electrically insulating substance 11. In the light valve substrate type semiconductor device, although not shown in the drawings, a liquid crystal is provided below the pixel portion, and light is transmitted through the liquid crystal. When this light is applied to the switching transistor and many transistors in the driver circuit section, the electron-hole pairs excited by the light become a leak current, deteriorating the element characteristics. The chromium film 117 provided below the electrically insulating material is provided to prevent light from being irradiated to each transistor.

Reference numeral 118 denotes a passivation film made of a plasma nitride film, 119 denotes a transparent adhesive, and 120 denotes a transparent quartz substrate or glass plate. A method for manufacturing a semiconductor device for a light valve substrate according to the present invention will be described with reference to the process sectional views of FIGS. 71 is a thick single crystal silicon substrate having a thickness of about 600 μm, 72 is a silicon oxide film having a thickness of about 1 μm,
Reference numeral 73 denotes single crystal silicon having a thickness of about 1 μm. These three-layer silicon wafers are generally used for SOI (Silicon On Silicon).
Insulator: Silicon on insulator) wafer. The semiconductor device for a light valve substrate of the present invention forms a switching transistor group for selectively supplying power to a driver circuit and a pixel driving electrode in a thin single-crystal silicon layer 73 through a normal IC manufacturing process. As shown in FIG. 1, a transparent glass substrate 120 is provided by a transparent adhesive 119.
And the thin single-crystal silicon 73 side, and finally the thick single-crystal silicon substrate 71 is removed. FIG. 7 shows a very early stage of the IC manufacturing process. In FIG. 7B, a resist 74 is applied. FIG.
In (c), after exposure and development, the resist on the region that will become a pixel portion in the future is removed. In FIG. 7D, the single crystal silicon layer at a portion where the resist has been removed by dry etching is etched by a certain thickness. FIG. 7E is a process sectional view of the semiconductor device of the present invention after the resist 74 is removed. S on the left side of the drawing
The thickness of the OI layer 75 is t _s1 , the thickness of the right SOI layer 76 is t _S2 , and t _S1 is larger than t _s2 . In a subsequent step, a driver circuit is provided in the SOI layer 75 on the left side of the drawing.
A switching transistor group for selectively supplying power to the pixel electrode is formed in the SOI layer 76 on the right side of the drawing.

Another embodiment of the method for manufacturing a semiconductor device for a light valve substrate according to the present invention will be described with reference to the process sectional views of FIGS. 8 (a) to 8 (g). In FIG. 8A, reference numeral 81 denotes a thickness of about 600
μm thick single crystal silicon substrate, 82 has a thickness of about 1 μm
And 83, a single crystal silicon layer (SOI layer) having a thickness of about 1 μm. The three layers form an SOI wafer. This SOI wafer is thermally oxidized to form a silicon oxide film SiO ₂ 84 having a thickness of several hundreds of square meters.

Next, as shown in FIG.
After depositing a silicon nitride film 85 of 500 °, a resist 86 is applied. As shown in FIG. 8C, the resist on the region where the switching transistor group for selectively supplying power to the electrode group of the pixel portion in the future is formed by the exposure and development processes, and the silicon at that portion is removed by dry etching. The nitride film is removed. As shown in FIG. 8D, the resist 86 remaining on the left side of the drawing is removed. FIG. 8 (e)
In the above, for example, by oxidizing,
A 1 μm thick silicon oxide film 87 is formed. On the left side of the drawing, a silicon nitride film 85 remains, which is not oxidized by this oxidation, and the thickness of the oxide film does not increase, and is several hundred
Remains. In FIG. 8F, the silicon nitride film 8 is formed.
5 is removed. Finally, in FIG. 8G, the thin silicon oxide film 84 and the thick silicon oxide film 87 are removed by a hydrofluoric acid solution.

As a result, as shown in FIG. 8G, the region on the left side of the drawing where the future driver circuit is formed is the region on the right side of the drawing where the driving transistor for the future pixel electrode having the thickness t _S1 is formed. , A region of single crystal silicon having a thickness of t _S2 is obtained. 7 (e) and 8 (g), for example, t _S1 is about 1 μm, and t _S2 is 0.2 to 0.5 μm.
m thickness.

[0027]

As described in detail above, in the semiconductor device for a light valve substrate according to the present invention, the thickness t _S2 of silicon in the region where the switching transistor for selectively supplying power to the pixel electrode group is formed is, for example, 0.1 _mm . Because it is as thin as 2-0.5 μm,
The leakage current of the switching transistor when irradiated with light is small, and the silicon thickness t _{S1 of the} region where the driving circuit for driving the pixel electrode is formed is relatively thick, about 1 μm. A single crystal silicon layer of about 0.5 μm or more still remains under the field oxide film, which has an excellent advantage that the substrate potential can be easily obtained and the drive circuit can easily operate.

[Brief description of the drawings]

FIG. 1 is a structural sectional view of a semiconductor device for a light valve substrate according to the present invention.

FIG. 2 is a perspective view showing a configuration of a semiconductor device for a light valve substrate.

FIG. 3 is a structural sectional view of a semiconductor device for a light valve substrate.

FIG. 4 is a structural sectional view of a switching transistor in a pixel portion.

FIG. 5 is a graph showing a relationship between a drain current and a gate voltage when light is irradiated and when light is not irradiated.

FIG. 6 is a graph showing the relationship between light leakage current and silicon thickness.

FIG. 7 is a process sectional view illustrating a manufacturing process of the semiconductor device of the present invention.

FIG. 8 is a process sectional view illustrating a manufacturing process of the semiconductor device of the present invention.

[Explanation of symbols]

 Reference Signs List 11 silicon oxide film 19 field oxide film 42 single crystal silicon 71, 81 single crystal silicon substrate 72, 82 silicon oxide film 73, 83 single crystal silicon layer 116 single crystal silicon layer under field oxide film 119 adhesive 120 glass substrate

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Tsuneo Yamazaki 6-3-1, Kameido, Koto-ku, Tokyo Seiko Electronic Industries Co., Ltd. (56) References JP-A-59-200288 (JP, A) Hei 3-7911 (JP, A) JP-A-62-223781 (JP, A) JP-A-4-219558 (JP, A) (58) Fields studied (Int. Cl. ⁷ , DB name) G02F 1 / 1362 G02F 1/1345 G02F 1/1333 H01L 29/78

Claims (2)

(57) [Claims] 1. A switch element group for selectively supplying power to a pixel electrode group and a drive circuit element group for selectively operating the switch element group are formed on a semiconductor silicon single crystal film on a film-like electrically insulating substrate. In the formed light valve substrate semiconductor device, the thickness of the semiconductor single crystal silicon layer in a region where the switch element group for selectively supplying power to the pixel electrode group is formed is a region where the drive circuit element group is formed A glass substrate that is thinner than the thickness of the single-crystal silicon layer of the above, and that is opposite to the electrically insulating substrate with respect to the pixel electrode group, the switch group, and the drive circuit element group via a passivation film and an adhesive. And a part of the driving element is arranged in the half.
The conductive silicon single crystal film is left, and the
Surface of the semiconductor silicon single crystal film over the
Connected to the high-concentration impurity region formed in
A part of the driving element and the semiconductor silicon on which the driving element group is formed.
The potential of the single crystal silicon film substrate is set to the same potential as that of the single crystal silicon film substrate, and the liquid crystal layer is disposed on the side opposite to the side where the single crystal silicon layer is formed with respect to the electrically insulating substrate. Semiconductor device for light valve substrate. 2. The light valve substrate semiconductor device according to claim 1, wherein said electrically insulating substrate is a silicon oxide film.